1. Field of the Invention
The present invention relates to an improved method of producing ceramic green tapes without using any organic solvent.
2. Description of the Prior Art
In general, ceramic green tapes, as noted by reference number 6 in FIG. 1, have in the past been prepared by dissolving a binder such as a butyral resin, an organic solvent-soluble acrylic resin or the like in an organic solvent such as methyl ethyl ketone, and mixing fine ceramic power with the solvent-resin mixture, followed by kneading of the resultant mass for an extended period of time to prepare a slip 2. Air entrapped in the slip is then removed and the slip in the device shown in FIG. 1 is passed through the lower portion of a so-called doctor knife 3 where it is deposited on a carrier film 4 to prepare a tape. Once the slip 2 is deposited, the tape is conveyed into a drying chamber 5 wherein it is heated to dryness.
However, because there are health problems associated with the use of organic solvents in the conventional preparative techniques, because the solvents result in offensive odors noticible by people living in the vicinity of the production facility and because there is an ever-present danger of explosion of vaporized solvent, new methods have recently been developed which employ an aqueous binder instead of an organic solvent. Among these methods is a manufacturing method (Japanese patent Laid-Open No. 113665/1980) which employs an aqueous polyurethane binder. This technique is attractive from the viewpoint that it makes it possible to obtain tough green tapes which feature a high charging density of the fine ceramic powder and a smooth surface. A need, however, continues to exist for an improved method of preparing green ceramic tapes of improved characteristics.